The invention relates to a bearing unit for material-web nip pulleys or pull rollers and, more particularly, for such nip pulleys or pull rollers which hold a material web under tension along the web path thereof and convey the material web through a folder, for example.
U.S. Pat. No. 5,738,620 is concerned with the mounting of pre-folding and pinch rollers in a folder. The diameters of the rollers are identical, and respective pairs of the rollers are arranged after one another, as viewed in the folding direction. The roller arrangement is rotatably accommodated between two side walls. One of the pre-folding rollers and one of the pinch rollers, respectively, are held stationary in position but can rotate at the two ends thereof in the side walls. The first pre-folding roller is rotatably mounted or journalled at the ends thereof, the bearings therefor being arranged on arms accommodated on the side walls. Connecting arms, whereon the second pinch roller is mounted, are likewise accommodated on the bearings of the first pre-folding roller. The connecting arms are spring-loaded perpendicularly with respect to the folding direction and are set against stops. The stops are accommodated in the side walls in a manner that the two pre-folding rollers and the two pinch rollers do not touch one another. Consequently, the corresponding bearings are relieved of any load. The folded copies emerging from the pre-folding rollers lift the connecting arms off the stops thereof and, by this movement, produce a gap having a width that depends upon the thickness of the folded copy. The gripping of the copy is thereby facilitated.
U.S. Pat. No. 5,738,264 discloses a device by which nip pulleys or pull rollers in the folder are automatically adjustable. Mutually opposing nip pulleys, one of which is stationary and the other is positionable relative to the latter, define an adjustable gap or nip between the respective peripheries thereof. The gap can be adjusted by a setscrew that is derivable by a servomotor. The revolutions of the setscrew are measured by a potentiometer assigned to the latter. Through the intermediary of a stop on the setscrew, the travel of the screw is limited. The rollers are thrown against one another, i.e., brought into mutual engagement, by a spring, but the spring also permits the movable nip pulley or pull roller for the material web to be thrown off or disengaged in the event of an overload. Through the intermediary of a sensor, the relative movements of the travel screw and stop to one another can be detected, signals from the sensor being used by a programmable control system to control the servomotor.
In the device disclosed in U.S. Pat. No. 5,738,264, an input provided by the operator is necessary in order then to produce automatically a match, which is triggered by the response of the sensor, of the gap widths between the surfaces of the pull rollers or nip pulleys.
It is accordingly an object of the invention to provide a A bearing unit for material-web nip pulleys or pull rollers which is a further development of the prior art and wherein an adjustment relative to one another of the pull rollers or nip pulleys which grip the material webs is effected independently of any intervention by the operator.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a bearing unit for throwing a movable nip pulley on and off a stationarily mounted nip pulley, having an actuating device for throwing the movable nip pulley laterally onto a material web, and having adjustable stops for adjusting actuating travel of the movable nip pulley, comprising a bearing plate whereon one of the adjustable stops is accommodated, a bearing foot having an anchorage, the bearing plate being movable around the anchorage of the bearing foot so as to be adjusted coaxially with respect to the anchorage, a prestressing element accommodated on the bearing plat, a bearing housing subjectible to a loading by the prestressing element, and a damping element actable upon the prestressing element.
In accordance with another feature of the invention, the actuating travel of the movable nip pulley is predefinable by the adjustable stops for determining relative movement between the bearing plate and the bearing foot.
In accordance with a further feature of the invention, the bearing plate is movable around the anchorage relative to the bearing foot.
In accordance with an added feature of the invention, the actuating device is disposed between the bearing plate and the bearing foot.
In accordance with an additional feature of the invention, the actuating device is activatable for pivoting the bearing housing about an articulation point on the bearing plate.
In accordance with yet another feature of the invention, the damping element is accommodated on the bearing plate, and the bearing housing is permanently subjected to a loading by the damping element.
In accordance with yet a further feature of the invention, the prestressing element is a spring accommodated between the bearing housing and the bearing plate.
In accordance with yet an added feature of the invention, the adjustable stops are used for varying prestressing force at the prestressing element.
In accordance with yet an additional feature of the invention, the damping element is a double-acting damping element.
In accordance with a concomitant aspect of the invention, there is provided a folder for processing material webs, having a bearing unit for throwing a movable nip pulley on and off a stationarily mounted nip pulley, including an actuating device for throwing the movable nip pulley laterally onto a material web, and adjustable stops for adjusting actuating travel of the movable nip pulley, the bearing unit comprising a bearing plate whereon one of the adjustable stops is accommodated, a bearing foot having an anchorage, the bearing plate being movable around the anchorage of the bearing foot so as to be adjusted coaxially with respect to the anchorage, a prestressing element accommodated on the bearing plat, a bearing housing subjectible to a loading by the prestressing element, and a damping element actable upon the prestressing element. prestressing element accommodated on the bearing plate, and a damping element actable upon the prestressing element.
The advantages inherent in the construction according to the invention are many and various.
Due to the permanent loading of the bearing housing, both with an adjusting force by a prestressing element and by the connection to a damping element, in the event of deflections, which, for example, may be caused by the passage of a relatively thick web splice, the movable roller is set back into the initial position thereof again, without requiring any intervention by the pressman; due to the nip-pulley or pull-roller configuration according to the invention, a lower sensitivity of the pair of nip pulleys or pull rollers is achieved, even during the passage of disruptive or faulty locations in the nip-pulley or pull-roller gap. With the mounting of the movable pull rollers or nip pulleys according to the invention, the web tension may be kept constant better, which is beneficial to the maintenance of the cutting register.
Furthermore, with the construction according to the invention, there is no longer any need for the pressman to perform a fine adjustment manually if the grammage of the web or the page combination pattern should change.
In an advantageous development of the idea upon which the invention is based, the movement of throwing the movable pull roller or nip pulley onto the material web can be achieved by a relative movement between a bearing foot and a bearing plate that is mounted coaxially with respect to the latter, it being possible for the relative movement to be predefined by adjustable stops. By an actuating device disposed between the bearing plate and the bearing foot, the adjusting movement may be impressed upon the bearing housings that accommodate the pull rollers or nip pulleys.
By connecting the bearing housing to a damping element that acts in both directions, i.e., is double-acting, it is additionally possible to prevent the build-up of oscillations at the bearing housing about the respective articulation point thereof on the lower extension of the bearing plate, so that when faults or splices in the material web pass through, the constant web tension can be maintained, and a build-up of oscillations of the movable pull rollers or nip pulleys resulting from the faults or splices, does not occur. Fluctuations in the web tension are mostly associated with fluctuations in the cutting accuracy of the material webs at the pair of cutting cylinders. This is followed by fluctuations in the quality of the copies to be separated from the material web, so that the maintenance of a constant web tension, even during the passage of faults or splices, continues to be assured, which is essential for the maintenance of a high product quality in the folder.
The engagement or throwing force of the movable pull roller or nip pulley onto the material web may be adjusted by a prestressing element, for example, in the form of a helical spring, so that the respectively optimum adjusting force can be set in accordance with the web thickness in the case of single-ply or multi-ply web runs.
The bearing unit according to the invention may advantageously be used for throwing-on and throwing-off, i.e., engagement and disengagement, movements, respectively, of a movable pull roller or nip pulley in conventional folders and also in pinless folders. In both types of folders, ensuring a constant web tension is critical for a high product quality with high accuracy of cutting register.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a bearing unit for material-web nip pulleys or pull rollers, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: